High resolution Sea Surface Temperature and seawater oxygen isotope records in IODP Site U1389 during MISs 2 to 4

Abstract

<p>IODP Site U1389 recovered a thick contouritic drift sequence deposited on the main branch of the Mediterranean Overflow Water in the gulf of Cadiz. That allows high resolution core recoveries for Quaternary period. In this study a high-resolution SST record was obtained by modern analogues method, using planktic foraminifer assemblages and Artificial Neural Networks. Seawater oxygen isotope composition was inferred by using the <em>Globigerina bulloides</em> δ<sup>18</sup>O record and the new SST data.</p><p>During MIS-3 the average amplitude of the SST change between Greenland stadials and interstadials is in the order of 2 to 4 °C. Foraminifer taxa that best reflects these minor changes is <em>Globigeririnita glutinata</em>. Heinrich stadial periods are represented by abrupt SST drops of about 8 °C compared to Interstadial values, and high abundance of polar and subpolar species <em>Neogloboquadrina pachyderma</em> <em>sin </em>and <em>Turborotalita quinqueloba</em>. During MIS-2 and MIS-4, SST is higher than expected for glacial maxima, with some subtropical species occurrence except in Heinrich events. Seawater δ<sup>18</sup>O also shows millennial variability, with higher values during Greenland Interstadials and the most pronounced drops or freshening in Heinrich stadial events. During glacial maxima stadials δ<sup>18</sup>O reaches its highest values, that reflects together with the high SST potential subtropical influence.</p><p>SST and seawater δ<sup>18</sup>O changes along the record precisely reflect the impact of the Greenland stadial-interstadial events and Heinrich events on sea surface conditions. Minor event Heinrich 2.2 (2b) has been identified by SST drop but not by water freshening. Otherwise, Greenland stadial 15, which corresponds to C-14 IRD event in North Atlantic shows Heinrich-like behavior according to both sea surface proxies.</p>